It is thus the object of the present invention to create a device for boundary layer suction with a composite component that forms the surface where drawing off by suction can take place, and to create a respective manufacturing method that makes it possible, with little expenditure and with reproducibly high quality, to efficiently manufacture a robust surface where drawing off by suction can take place.
The invention includes the device-related teaching according to which the surface where drawing off by suction can take place is formed by at least one panel-shaped composite component comprising an extruded profile of light metal as a base body, which extruded profile represents several suction channels open towards the outer skin, onto which base body, for the purpose of forming the outer skin, a micro-perforated metal cover sheet has been applied in the region of the surface where drawing off by suction can take place.
The solution according to the invention provides, in particular, an advantage in that by means of this composite component that is simple to manufacture a surface of any size and shape can be produced, from which surface drawing off by suction can take place. Because of the extruded base body the composite component is very stable, and the manufacturing method of extrusion molding ensures reproducibly high quality. Extrusion molding provides another advantage in that light metal can be used as a material, so that the composite component overall is of quite lightweight construction. Furthermore, with the use of the extruded profile there is no welding work involved, which is otherwise quite elaborate, to form the suction channels underneath the outer skin in the region of the surface where drawing off by suction can take place, and consequently the manufacturing time is also reduced.
Preferably, the suction channels, which have been formed according to the invention, of the surface where drawing off by suction can take place in the extruded profile should extend side by side so as to be spaced apart from each other in the direction of the wingspan of the aerodynamic component of the aircraft, which applies to so-called constant-chord profiles. Such a direction provides the composite component not only with mechanical stability but also with a favorable channel layout for efficient boundary layer suction.
In the case of a commercial aircraft the aerodynamic component on which the surface where drawing off by suction can take place is arranged can be the engine nacelle and/or the wings and/or the vertical stabilizer. Boundary layer suction in these aerodynamic components results in a significant reduction in the frictional resistance of the commercial aircraft, in that in those regions the favorable laminar flow is maintained.
According to a measure that improves the invention, it is proposed that for balancing the air mass flow an aperture be inserted into the suction line, which is preferably formed by the interior of the aerodynamic component, between the surface where drawing off by suction can take place and the suction source. By way of the size of the aperture the negative pressure acting on the surface where drawing off by suction can take place can be regulated in order to ensure efficient boundary layer suction with simple technical means. While as a rule it is not necessary to vary the throttle cross section, it is however also imaginable to regulate the air mass flow with an adjustable throttle instead of with an aperture.
The base body, which is preferably made as an extruded profile from the light metal aluminum or from an aluminum alloy, is to comprise a micro-perforated metal cover sheet preferably made from titanium or stainless steel in order to form the composite component. In titanium in a titanium alloy, or in stainless steel it is not only possible to place the micro-perforation in a simple manner from the point of view of production technique, but these preferred metals are also adequately corrosion-resistant for the application that forms the subject of the invention, in the region of the outer skin of the aircraft.
According to another aspect of the invention, the micro-perforated metal cover sheet is preferably firmly bonded or galvanized onto the extruded profile in the region of the open channels, with such bonding or galvanizing preferably taking place by means of a pulse-current method.
To manufacture such a rigid integral connection, the stringer heads of the extruded profile, which stringer heads establish contact with the metal cover sheet, are mechanically processed, for example by milling, in order to provide a very planar supporting surface for the metal cover sheet. This provides favorable prerequisites for subsequently establishing the integral connection so that finally a stable panel-shaped composite component results.
According to a further measure that improves the invention, it is proposed that micro-perforation be produced only after the metal cover sheet has been placed onto the extruded profile, namely preferably by laser beam drilling. Accordingly it is not necessary to produce micro-perforation prior to integrally connecting the metal cover sheet to the extruded profile.
In the case of, preferably subsequent, production of micro-perforation in the metal cover sheet, only those regions of the surface need to be perforated behind which there is an open suction channel. Thus, advantageously, the surface regions behind which there is a stringer head of the extruded profile can be left non-perforated so that the integral connection is not negatively affected by the micro-perforation. In this way micro-perforated suction channels arise, which preferably extend in the direction of the wingspan, for local boundary layer suction.
If the region of micro-perforation is to be enlarged to provide an improved suction removal effect, according to another advantageous improvement aspect of the invention it is proposed that the stringer heads of the extruded profile be chamfered so that a larger effective suction removal surface arises.
The integral connection, which has been produced by bonding or galvanizing the metal cover sheet onto the mechanically pre-processed extruded profile, generates a stable composite component. In the case of bonding it is proposed that an epoxy resin adhesive be applied to the stringer heads of the extruded profile, and subsequently the metal cover sheet be put in place under pressure. After the adhesive has cured, an even, rigid, adhesive connection exists that is to be provided with corrosion protection. If the integral connection is instead to be produced by galvanizing, it is proposed that the extruded profile in the region of the open suction channels first be filled with an electrically conductive wax. Depending on the spacing of the stringer heads this can also take place by inserting a wax-enclosed solid core in order to save wax material. After completion of galvanizing, the wax is to be removed by the application of heat.